Tensioning device for wide moving belts

ABSTRACT

A tensioning device for a steel conveyor belt running over a drum or pulley which insures uniform tension over the entire width of the belt to prevent cracking the belt due to concentrated stress. The device comprises hydraulic cylinders, one at either end of the drum axle to adjust tension by moving the drum, and a regulating cylinder acting on the axle in a direction perpendicular to the force of the tensioning cylinders which responds to lateral deflections of the belt and tilts the drum to cause the belt to return to its normal mean position. The tensioning cylinders are connected to a common fluid supply conduit of larger diameter than the conduit connecting to the source of fluid to insure equal pressure in both cylinders in any tilted position.

United States Patent [111 aye/awe Ettel Nov. 6, 1973 TENSIONING DEVICE FOR WIDE MOVING BELTS Primary Examiner-Edward A. Sroka [75] Inventor: Hubert Ettel, Teichhutte/Harz, Atmmey GeOrge Newm et Germany [73] Assignee: Wilhelm Mende & C0., [57] ABSTRACT Teichhutte/Harz, Germany A tensioning device for a steel conveyor belt running [22] Filed: Mar. 21, 1972 App]. No.: 236,690

FOREIGN PATENTS OR APPLICATIONS 9/1967 Germany 226/21 over a drum or pulley which insures uniform tension over the entire width of the belt to prevent cracking the belt due to concentrated stress. The device comprises hydraulic cylinders, one at either end of the drum axle to adjust tension by moving the drum, and a regulating cylinder acting on the axle in a direction perpendicular to the force of the tensioning cylinders which responds to lateral deflections of the belt and tilts the drum to cause the belt to return to its normal mean position. The tensioning cylinders are connected to a common fluid supply conduit oflarger diameter than the conduit connecting to the source of fluid to insure equal pres sure in both cylinders in any tilted position.

3 Claims, 2 Drawing Figures 1 TENSIONING DEVICE FOR WIDE MOVING BELTS This invention relates to a tensioning device for wide strip which passes over a tensioning roll whose axle is prestressed on each side by a hydraulic tensioning cylinder in the direction of tension of the strip, the tensioning cylinders being connected by means of supply conduits to a source of pressure medium where furthermore in addition to the hydraulic tensioning cylinder there is provided on one side of the roll a hydraulic regulating cylinder acting on the axle in a substantially perpendicular direction to the direction of force of the hydraulic tensioning cylinder and which is supplied with a pressure medium as a function of the lateral deflections of the strip in such a manner that tilting of the roll causes the strip to be returned into its mean position.

A tensioning device for steel strip is known in which hydraulic tensioning cylinders press against the ends of the shaft of the tensioning roll and thus prestress the latter in the direction of tension. In order to compensate for any lateral deflection of the steel strip the axis of the tensioning roll is subjected at one end to an additional load from a regulating cylinder whose direction of force is perpendicular to that of the adjacent tensioning cylinder. The regulating cylinder is supplied with a pressure medium as a function of the deflections of the steel strip. The deflections are detected by a sensing device which is irrelevant in this context, and converted into corresponding pressure signals which act on the regulating cylinder. It has been found in The object of the present invention is to provide a device for tensioning a strip whereby cracking of the strip, more especially of a steel strip, is prevented.

The problem of the present invention is solved by joining the two hydraulic tensioning cylinders by means of an equalising conduit.

The solution according to the present invention is based on the fact that the regulating movements of the regulating cylinder may be very great, especially if the strip should be deflected rapidly as may be caused, for example, by a sudden cold draught of air. Since the regulating of the central path of the steel strip is basically effected by the tilting of the tensioning roll, great stresses are produced in the peripheral zone of the steel strip. During the regulating process this peripheral zone must absorb, in practice, the entire stresses of the strip which during normal running would be absorbed by the total width of the steel strip. Thus cracks are formed which may then easily be propagated due to the notch effect over the entire width of the strip.

The teaching of the present invention is directed in such a way as to ensure a very uniform stress load over the entire width of the strip even under a regulating movement. For this purpose a direct connecting conduit is provided between the hydraulic tensioning cylinders which permits a very rapid equalisation of the pressure medium so that both ends of the tensioning cylinders and thus the strip must always be uniformly stressed over its entire width.

In the solution according to the present invention it is not necessary to provide each tensioning cylinder with its own supply conduit from a source of pressure medium. One conduit for the pressure medium suffices and it may be very thin, even thinner that the equalising conduit between the tensioning cylinders, thus considerably simplifying the apparatus.

If the equalising conduit is considerably larger than the supply conduit the rate of equalisation of the pressure medium in the equalising conduit and thus the accelerations, are slow so that the regulating movements of the regulating cylinders will cause a rapid equalisation by the tensioning cylinders of the changes in the stress of the strip over its entire width.

Although in practice it is most convenient to usehydraulic tensioning cylinders, it may also be suitable to use the corresponding mechanical equivalent in the form of a balance beam whose ends support the ends of the shaft of a tensioning roll and whose centre is supported.

The invention will be illustrated in more detail by an embodiment as shown in the drawings where FIG. 1 is a right side view of a preferred embodiment of the present invention.

FIG. 2 is a cross-section of the preferred embodiment of the present invention shown in FIG. 1 taken along 11-.

Referring to FIGS. 1 and 2, a steel strip 1 is passed over a pair of deflecting rolls 2, 3 and a tensioning roll 4. The tensioning roll 4 includes a shaft or axis 5.

A pair of tensioning cylinders 7, having plungers 6, act upon the ends of the shaft 5. As indicated eariler, the tensioning cylinders 7 prestress the steel strip 1 to the desired tension.

The tensioning cylinders 7 are connected by means ofa pressure equalizing conduit 8. The pressure equalizing conduit 8 is connected by a supply conduit 9 to a pressure source (not shown) which supplies the pressure necessary to operate the tensioning cylinders 7. The diameter of the pressure equalizing conduit 8 is large compared to the diameter of the supply conduit 9 to ensure that there is always equal pressure in the tensioning cylinders 7.

Additionally, a regulating cylinder 10, having a plunger 11, acts upon one end of the shaft 5. The regulating cylinder 10 acts in a direction substantially'perpendicular to the direction of action of tensioning cylinders 7. A regulating conduit 12 connects the regulating cylinder 10 with a variable pressure source (not shown).

The pressurization of the regulating cylinder 10 varies according to the deflection of the steel strip 1 from its central path. This deflection is measured by any conventional detecting means. In this manner, the tensioning roll 4 is tilted as a function of the path of the steel strip 1, such that the steel strip 1 is returned to its central path.

The tilting of the tensioning roll 4, however, also changes the stress pattern exerted by the tensioning roll 4 on the steel strip 1, and the new stress pattern may cause cracking in the peripheral zones of the steel strip 1. According to the present invention, this cracking problem is substantially avoided by means of pressure equalizing conduit 8, which ensures that fundamentally the same pressure prevails in both tensioning cylinders 7. Thus, regardless of the orientation of the tensioning roll 4, the steel strip 1 is subjected to the same stress over its entire length.

I claim:

l. in a tensioning device for conveyor belts, said tensioning device including a tensioning roll, said conveyor belt passing over and having a mean path on said tensioning roll, a pair of hydraulic cylinders, said tensioning cylinders being connected to a pressure source by a supply conduit and acting upon said tensioning roll to adjust the tension exerted by said tensioning roll upon said conveyor belt, and a hydraulic regulating cylinder, said hydraulic regulating cylinder acting upon one end of said tensioning roll in a direction substantially perpendicular to the direction of action of said hydraulic tensioning cylinders, said hydraulic regulating cylinder being connected to a pressure source and pressurized as a function of the lateral deflection of tween said hydraulic tensioning cylinders. 

1. In a tensioning device for conveyor belts, said tensioning device including a tensioning roll, said conveyor belt passing over and having a mean path on said tensioning roll, a pair of hydraulic cylinders, said tensioning cylinders being connected to a pressure source by a supply conduit and acting upon said tensioning roll to adjust the tension exerted by said tensioning roll upon said conveyor belt, and a hydraulic regulating cylinder, said hydraulic regulating cylinder acting upon one end of said tensioning roll in a direction substantially perpendicular to the direction of action of said hydraulic tensioning cylinders, said hydraulic regulating cylinder being connected to a pressure source and pressurized as a function of the lateral deflection of said conveyor belt from said mean position, such that said tensioning roll is tilted causing said conveyor belt to return to said mean position, the improvement comprising an equalizing conduit connecting said hydraulic tensioning cylinders, said equalizing conduit equalizing the pressure in said hydraulic tensioning cylinders to provide a uniform tension across said conveyor belt.
 2. The improvement of claim 1 wherein the diameter of said equalizing conduit is substantially greater than the diameter of said supply conduit.
 3. The improvement of claim 1 wherein said supply conduit is connected to said equalizing conduit between said hydraulic tensioning cylinders. 